1. FIELD OF THE INVENTION
This invention relates generally to control valves and more particularly to an electrically operated fluid control valve having a torque motor for synchronized control of inlet and outlet valve members to provide a controlled output pressure while protecting sensitive diaphragms from excess differential pressure.
2. BRIEF DESCRIPTION OF THE PRIOR ART
Control valves are known in the art. There are several patents which disclose various control valves.
Duder et al, U.S. Pat. No. 4,535,810 discloses an electrically controlled valve using a piezio electric strip as an actuator which when actuated by an electric signal moves with respect to openings in the pressure and return chambers to cause an increase or decrease in pressure in the respective load passages in communication with the chambers.
Kolze, U.S. Pat. No. 4,527,590 discloses an A.C. solenoid operated valve having a single inlet and dual outlets with lever means pivotally disposed in a valving chamber and having poppets which alternately open and close one outlet while the other remains open upon movement of the lever. An external solenoid coil moves an armature disposed in the chamber which effects the lever movement.
Ruby, U.S. Pat. No. 4,131,130 discloses a pneumatic control valve of the flapper type which controls pressure within a chamber from two sources of pressure in proportion to an electrical control signal. A flapper is associated with a nozzle connected with each source and the flappers are resiliently coupled to a common electrically actuated armature.
Nash, U.S. Pat. No. 3,242,945 discloses a change-over valve comprising a pair of valve chambers each having inlet and outlet ports and an exhaust opening. The cojoined valve bodies are moved so that they alternately seal off the inlet port and exhaust opening of their respective chambers.
Hartley, U.S. Pat. No. 3,994,314 discloses a servo pressure regulator comprising a regulated pressure chamber and first and second ports leading thereto. The first and second ports are adapted to communicate with fluid at first and second pressures, respectively. The valves are folded resilient strips held against the passages or conduits. A first valve controls fluid flow between the first port and the regulated pressure chamber, and a second valve controls fluid flow between the second port and the regulated pressure chamber. The valve associated with the vacuum port is held against the port by the differential pressure, and the valve associated with the pressure port is urged away from the pressure port. A preregulator controls the pressure in the first port to maintain the pressure drop across the first valve no greater than about the first magnitude.
The present invention is distinguished over the prior art in general, and these patents in particular by an electrically operated fluid control valve which provides a controlled output pressure proportional to an electrical control signal. The valve housing has a pressure control chamber, an inlet passageway leading from an inlet port to the chamber, an outlet port connected to the chamber, and an outlet passageway leading from the chamber to an exhaust port. A supply diaphragm coupled with a supply valve at the inlet port regulates fluid pressure supplied to the chamber through the inlet passageway and another passageway communicates fluid pressure from the chamber to the supply diaphragm. An exhaust diaphragm at one end of the chamber coupled with an exhaust valve at the exhaust port regulates fluid pressure supplied to the exhaust port and the outlet passageway communicates fluid pressure between the chamber and the exhaust diaphragm. A torque motor in the housing rotates a control arm in the chamber to move an adjustable inlet control/relief valve in the inlet passageway to control the flow of fluid pressure between the inlet passageway and the control chamber or an adjustable outlet control/relief valve in the outlet passageway to control the flow of fluid pressure between the outlet passageway and the control chamber. The inlet control/relief valve and the outlet control/relief valve are moved proportional to the applied current and meter the flow of regulated pressure into the control chamber and the outlet port to provide a controlled output pressure through the outlet port and protect the diaphragms from excess differential pressure.